The present invention relates to a system and processes concerned with the separation of tar from sand and tar shale.
Tar sand deposits exist in many places throughout the world. Perhaps the largest tar sand deposit is in Athabasca, Northern Alberta. For the last twenty years or more, attempts have been made to separate the tar or bitumen deposits from the sand. None of these have proved economically feasible because of the costs that are involved in the different processes. The type of processes attempted include heating the tar sand mixture, freezing the mixture, and adding solvents to the tar sand mixture. All attempts have generally involved the introduction of more energy than is feasible or economical to separate the tar from the sand. In some cases, tar is found in rock shale formations and it is first necessary to crush the rock before any attempts to separate the tar from the shale. Throughout this specification the term tar sand includes crushed tar shale.
Another type of process that has been attempted is the mechanical separation of tar and sand. One example of the mechanical separation process has been illustrated in U.S. Pat. No. 3,891,550 which issued on June 24, 1975 to Gray et al. This process involved compressing or compacting tar sand against a rotating oleophilic surface so as to form a layer on that surface. Then under the influence of the attraction of tar to the oleophilic surface and centrifugal forces, the sand separates from the tar and is dislodged from the surface, leaving the tar to be scraped off the surface.
Tar sand is generally found with each particle of sand having a coating of tar and water surrounding it. The problem is to remove this coating of tar and water and then separate the tar from the water. If it was merely a question of just removing the tar from the sand this would be a great deal simpler, however, the tar and water separating from the sand also retains a small quantity of clay and it is this combination of tar, water and clay which is hard to separate.